In an electronic imaging device such as a laser printer, a laser photocopiers, a facsimile apparatus, etc., a process cartridge is normally installed detachably, which is used for developing electro-static latent image and comprised at least of one or more components of developing roller, photosensitive drum, toner feeding roller, agitator, doctor blade and charging roller. During operation of the electronic imaging device, printing operation is realized by driving the corresponding components in the process cartridge.
There are two major driving methods at present for the process cartridge. In one method, as disclosed in U.S. Pat. No. 4,829,335, a spiral gear provided in the driving part of the printer is engaged with a spiral gear as a driving-force transmitter provided at one end of the photosensitive drum, by which the photosensitive drum is rotated. In the other method, as disclosed in Chinese patent of invention No. CN1217241C, a non-twisted protrusion as a driving-force transmitter protruding from one end of the photosensitive drum is engaged with a coupling twisted hole provided in the driving part of the printer to receive and transmit the driving force, by which the photosensitive drum is rotated.
In the second method, under the action of torque, transmission between the non-twisted protrusion at the end of the photosensitive drum and the coupling twisted hole in the driving part generates an axial force which separates them from each other along the axial direction, effect the fit quality between the twisted hole in the driving part and the non-twisted protrusion from the photosensitive drum, decrease transmission stability and reliability as well as printing quality; with the increasing of operating time, interrupt the torque transmission by accidental disengagement between the driving part and the photosensitive drum.